Tamping arrangement for supplying a material to crushing rollers



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. RETTENMAIER TO CRUSHING ROLLERS Filed July 28, 1964 TAMPINGARRANGEMENT FOR SUPPLYING A MATERIAL Sept. 12". 1967 United StatesPatent 3,341,137 TAMPING ARRANGEMENT FOR SUPPLYING A MATERIAL TOCRUSHING ROLLERS Josef Rettenmaier, Holzmuhle Gemeinde, Rosenberg,

Germany, assignor to J. Rettenmaier & Siihne, Holzmuhle, Rosenberg uberEllwangen, Jagst, Germany Filed July 28, 1964, Ser. No. 385,674 Claimspriority, application Germany, July 31, 1963, R 35,803 13 Claims. (Cl.241-222) The present invention relates to an apparatus for supplyingrelatively small particles to the gap between a pair of rotary crushingrollers, and more particularly to apparatus for further reducing thesize of the small particles.

It is known to reduce the size of the small particles by moving a massof such particles through the gap between cooperating crushing rollers.Under practical conditions, considerable difiiculties develop. In theevent that the gap is relatively small, a comparatively large mass ofparticle accumulates in the bight of the rollers above the gap, and therollers are incapable of gripping the compressed and lumpy mass. On theother hand, if the gap is relatively wide, the desired reduction of sizeof the particle is not achieved.

It is the object of the present invention to overcome the disadvantagesof methods and apparatus for reducing the size of small particles, andto supply relatively small particles to the gap between a pair ofcrushing rollers in such a manner that the size of the particles isfurther reduced by the action of the crushing rollers.

Another object of the invention is to subject a mass of particles fed tothe gap between a pair of crushing rollers at a periodically varyingpressure.

Another object of the invention is to prevent the formation of acompressed and lumpy mass of small particles in the bight betweencrushing rollers by subjecting the mass to a periodically varyingpressure acting in the direction of the gap.

Another object of the invention is to transport precompressed smallparticles periodically into the gap between a pair of crushing rollers.

With these objects in view, the present invention is advantageouslyapplied to small particles, such as wood shavings, small pieces of plantpeels or nut shells, or mixtures of different kinds of small particles.The mass of small particles is supplied to the bight on top of at leastone pair of cooperating crushing rollers, so that it accumulates andtends to pass into the gap due to gravity. In accordance with thepresent invention, a pressure exceeding the gravity is applied to themass of small particles accumulated and confined in a space before thegap, for example, mechanical pressure may be applied. In this manner,the mass of small particles is pressed into the gap, and in accordancewith the preferred embodiment of the invention, the pressure is appliedin the direction of the gap and periodically varied, for example byreciprocation of a stamping or tamping means in a closed passage intowhich the mass is fed.

By the periodically and rhythmical variation of the pressure, lumpformation and sticking together of the small particles of the fed massis avoided.

The desired reduction of size of the particles is favorably influencedif the crushing rollers are resiliently mounted for movement toward andaway from each other so that the width of the gap varies when thepressure is periodically increased and decreased, permitting thetransport of the mass of particles through a relatively small gap whilebeing subjected through the action of the crushing rollers.

An improvement of the desired result is achieved at 3,341,137 PatentedSept. 12, 1967 any frequency or rhythm of the pressure increases, but itis preferred to select the frequency of the pressure variation and theperipheral speed of the crushing rollers in such a manner that thecrushed par-ticles flow away from the crushing roller in a substantiallyuniform stream with relatively small fluctuations.

To achieve this result, it is advantageous to use crushing rollershaving a diameter between 200 mm. and 300 mm., and to rotate thecrushing rollers at a low speed, for example at 40 revolutions perminute.

The results of the present invention are particularly favorable if themass is accumulated in a confined space adjacent the bight between therollers in a pre-compressed condition, since in this event the pressurevariations act on a precompressed material so that the same enters thegap between the rollers in compressed condition.

An apparatus according to the invention comprises a tamping means whichis reciprocable in the direction of the gap between a pair of crushingrollers, and feeding means for feeding a mass of small particles to thebight on one side of a gap between the crushing rollers. A tamping meansreciprocates preferably in a closed passage into which the feeding meanssupply the small particles, so that the reciprocation of the tampingmeans periodically varies the pressure acting on the mass of accumulatedparticles in the region of the gap, the pressure changing between amaximum achieved when the tamping means moves toward the gap, and aminimum, that is substantially zero, when the tamping means moves awayfrom the gap. Due to the reciprocation of the tamping means, not onlythe pressure is varied, but at the same time, a feeding of the mass ofparticles in the region directly before the gap is accomplished, sinceevery time the tamping means moves away from the gap and forms an emptyspace, another amount of the mass of particles is fed by the feedingmeans to fill the empty space, and such newly fed amount is then fedinto the gap between the crushing rollers by the forward reciprocatingstroke of the tamping means. Consequently, a mixing of the mass ofparticles takes place at the same time, sothat formation of lumps andsticking together of the particles is prevented.

The reciprocating motion of the tamping means is designed so that theleading operative end of the tamping means moves into the closeproximity of the'gap, without touching the surface of the crushingrollers. Consequently, a thin layer of the mass of particles remainsunder all operational conditions between the crushing rollers and thetamping means.

The effect of the tamping means is substantially improved if its leadingoperative face is disposed perpendicularly to the direction of movementof the tamping means, and has a shape corresponding to the shape of thegap, for example an elongated rectangular shape. In this event, thetamping means is a plate and the operative end face has a lengthcorresponding to the axial length of the crushing rollers, and a widthor thickness corresponding to the width of the gap.

In this manner, a substantially uniform effect of the tamping plate onthe accumulated mass is achieved, and the pressure along the entire gapvaries uniformly between a maximum and a minimum within the part of themass located in the region for the gap. A plateshaped tamping means hasthe advantage that no parts of the accumulated mass of particles ispulled back during the return stroke of the tamping plate, particularlyif the tamping plate is guided between guide walls. This may be eifectedwith the aid of leaf springs mounted on one hand on a stationary housingpart and on the other 'hand on the tamping plate, the resiliency ofsprings betamping plate remains possible. A straight motion is bestetfected by guiding the tamping plate not only between the straightwalls of the passage leading to the gap, but also by pairs of guidingrollers abutting the lateral faces of the tamping plate.

The mass of particles is fed in the direction transverse to thedirection of reciprocating movement of the tamping plate, preferablythrough a duct having a discharge end in the region of the tamping plateso that the mass of particles is pressed against a lateral face of thetamping plate when the same is in the advanced position. Sealing meansare provided between the discharge end of the sealing duct and thetamping plate to maintain a high pressure in the accumulated mass.

Transporting screws are disposed in the feeding duct, preferably inparallel positions, and dead spaces between the transporting screwsadvantageously taken up by ribs secured to the upper and inner walls ofthe duct. The transporting screws compress the mass of small particles,particularly in the passage in which the tamping plate reciprocates, sothat the mass is in compressed condition when engaged and transported bythe advancing tamping plate. In order to obtain the best transportingand feeding condition, it is advantageous to provide bearings only forthe ends of the transporting screws remote from the discharge end of theduct, and to drive only these rear ends of the transporting screws.

In order to prevent leaking of the compressed mass, it is preferred toarrange the reciprocating motion of the tamping means in such a mannerthat the tamping means in its uppermost position farthest spaced fromthe gap is still located at the upper end of the passage in which thetamping plate moves, and preferably only at the middle of the passage.The discharge end of the feeding duct opens into the passage, and isuncovered in the retracted position of the tamping plate.

The passage is bounded on the side of the tamping means remote from thefeeding duct by a wall slidingly engaged by the tamping plate so thatthe entire passage before the gap is closed and sealed whereby the massof particles located in the passage under the tamping plate ismaintained in compressed condition.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a fragmentary sectional view illustrating one embodiment ofthe invention;

FIG. 2 is a fragmentary sectional view taken on line 22 in FIG. 1; and

FIG. 3 is a fragmentary perspective view illustrating the leadingoperative end of a tamping plate on an enlarged scale.

Referring now to the drawings, a support or housing supports in itslower portion a pair of crushing rollers 11 and 12 which are mounted onshafts 13 and 14 carried by bearings 15 and 16, each of which issubjected to the pressure of resilient means 19 and 20 to urge thecrushing rollers toward each other so that gap between crushing rollers11 and 12 is of variable width.

Receiving container means 26 are provided below crushing rollers 11 and12 to receive material crushed and reduced in particle size by rollers11 and 12.

Housing 10 supports a hopper 30 in which a mass of small particles whichare to be reduced in size is placed. The lower conical end 33 of hopper30 is connected by vertical conduit 35 to a duct 37 in housing 10. Thelength of duct 37 corresponds to the axial length of rollers 11 and 12,and consequently to the length of gap 25. The height of duct 37 isselected so that a plurality of transporting screws 40 can be disposedin duct 37 adjacent and parallel to each other to feed particlessupplied through conduit 35 toward the region of the gap between thecrushing rollers, but located above the same. Shafts 44 of thetransporting screws are mounted in bearings 42 only at one end, and amotor 43 is mounted in a lower cavity of housing 10 and drives throughgears 45 and 46, a gear 48 on one of the shafts 44. Each shaft 44carries a gear 48, and idle pinions are located between each pair ofgears 48 meshing with the same so that all gears 48 and shafts 44 rotatein the same direction.

A tamping plate 50 is disposed in a plane perpendicular to the planewhich is defined by the axes of shafts 13 and 14 about which thecrushing rollers rotate. Tamping plate 50 is connected to pin means 56on eccentric crank means 55 driven by motor means 54 so that tampingplate 56 is reciprocated between the advanced position shown in FIG. 1and a raised retracted position.

The upper end of tamping plate 50 is guided between a plurality of guidemeans, each of which includes a pair of guide rollers 61 engagingopposite lateral faces of tamping plate 50, and being mounted onbrackets 60 secured to housing 10. The lower end of tamping plate 50 isguided in a passage which includes on one side of the tamping plate awall 64 and a sealing means 63 between wall 64 and the lateral face ofthe tamping plate, and on the other side a wall 66 and a sealing means67. Walls 66 and 64, and end walls at the ends thereof form a passagefor tamping plate 50 into which the discharge end of feed duct 37 opens.A space 70 in the passage is formed in the raised retracted position oftamping plate 50 which is still located between walls 66 and 64, butuncovers the discharge end of duct 37. Since the surfaces at the bottomof housing 10 are closely spaced and parallel to the surfaces ofcrushing rollers 11 and 12, the lower end of the passage can beconsidered closed so that a closed space 70 is located between the gapand the leading lower operative end of the tamping plate, which has arectangular planar face 51, best seen in FIG. 3, and extending parallelto a plane passing through the axes of the crushing rollers. In thelower position of tamping plate 50, the discharge end of feed duct 37 isclosed, and face 51 is in the region of the gap, slightly spaced fromthe surfaces of the crushing rollers.

The apparatus operates as follows: An amount of small particles 31,which may be the result of a previous crushing operation, are filledinto hopper 30 and drop due to gravity through conduit 35, which extendsalong the length of the crushing rollers, into duct 37 which has acorresponding length. The particles fall between the threads of thetransporting screws 40 at the rear ends of the same, and are transportedthrough duct 37 toward the space 70. In the illustrated advancedposition of tamping plate 50 the material is pressed against a lateralface of the tamping plate and compressed. When due to the operation ofmotor means 54 the tamping plate 50 is raised and uncovers the dischargeend of duct 57, the material enters space 70 and is pressed against thesealing means 37 and wall 66 and into the space of the passage which waspreviously taken up by the lowered tamping plate. Since transportingscrews continue to rotate, the pressure of the fed mass is maintained,and when tamping plate 50 moves down toward the advanced position, thepressed material is pushed out of the passage and into gap 25 where itis crushed by the crushing rollers 11 and 12. The tamping plate 50 isagain retracted to a raised position uncovering the discharge end ofduct 37 so that another amount of particles 31 is pressed into space 70.The increased pressure of the downwardly moving tamping plate 50 maycause rollers 11 and 12 to slightly move apart to increase the width ofthe gap which is possible due to the provision of the resilientlymounted bearings 15 and 16.

In accordance with the present invention, the particles are not pressedinto the gap by the pressure of feeding means 40, but by the pressure ofthe independent tamping means 50 which causes a periodically varyingpressure acting on the mass of small particles accumulated in the regionof the gap to move into the gap so that the pressure in the gap varies.

The arrangement of the present invention permits a relatively slowrotary speed of the crushing rollers, and the speed may lie between 20and 50 revolutions per minute with 35 to 40 being a preferable speed forthe rollers 11 and 12. The diameter of the rollers depends on thecircumferential speed, and in connection with the aforementioned rotaryspeeds, the diameters of the rollers may be between 150 and 300 mm. anda preferred diameter is 220 mm. The width of the gap 25 between therollers 11 and 12 may range between .4 and 2 mm. and is preferably about1 mm. This gap depends on the production rate, i.e. the amount ofparticles passing the rollers, and furthermore on the surface texture ofthe rollers. The frequency of reciprocation of the tamping plate 50 is,as a rule, chosen rather high and is approximately between 800 and 1200and preferably about 1000 reeiprocations per minute.

The size of the particles to be processed may range between .1 and 5mm., while the hardness depends on the organic material used for theparticles. Wood, and other organic material like cellulose, straw, andWaste material of agricultural products can be used.

It will be understood that each of the elements described above or twoor more together may also find a useful application in other types ofcrushing methods and apparatus differing from the types described above.

While the invention has been illustrated and described as embodied inapparatus for supplying small particles at a periodically varyingpressure into the gap between a pair of rotating crushing rollers, it isnot intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed and desired to be secured by Letters Patent is:

1. An apparatus for reducing the size of particles, comprising, incombination, a pair of cooperating rotary rollers having parallel axesand defining a gap between each other; feeding means for feeding theparticles to said rollers and including a feed duct extending in adirection substantially parallel to a plane extending through said axesand having a discharge end located in the region of said gap so that amass of particles accumulates on one side of said rollers in the regionof said gap; a tamping means disposed at said discharge end on said sidereciprocable perpendicularly to said plane toward and away from said gapso that the mass is periodically urged into said gap; passage means forsaid tamping means having an opening forming said discharge end of saidfeed duct, said tamping means being movable between an advanced positionclosing said discharge end of said duct, and a retracted position inwhich the operative end of said tamping means is spaced from said gapuncovering said discharge end and still located in said passage andmeans for reciprocating said tamping means.

2. An apparatus as set forth in claim 1 wherein said tamping means is *aplate located in a plane passing through said gap perpendicularly to aplane extending through said axes; and wherein said discharge end ofsaid feeding duct is located in the close proximity of said plate; andincluding sealing means between said discharge end and said plate.

3. An apparatus as set forth in claim 1 wherein said operative end ofsaid tamping means in said retracted position is located substantiallyin the middle of said passage.

4. An apparatus for reducing the size of particles, comprising, incombination, a pair of cooperating rotary rollers having parallel axesand defining a gap between each other; feeding means for feeding theparticles to said rollers and including a feed duct extending in adirection substantially parallel to a plane extending through said axesand having a discharge and located in the region of said gap so that amass of particles accumulates on one side of said rollers in the regionof said gap; a tamping means disposed at said discharge end on said sidereciprocable perpendicularly to said plane toward and away from said gapso that the mass is periodically urged into said gap; a wall located onthe side of said tamping means remote from said discharge end of saidfeed duct for holding in the region of said gap particles fed throughsaid discharge end; and means for reciprocating said tamping means.

5. An apparatus as set forth in claim 4 wherein said wall engages saidtamping means in both end positions of the reciprocating movement of thesame; and sealing means between said wall and said tam-ping means.

6. An apparatus of the type described comprising, in combination, a pairof cooperating rotary rollers having parallel axes and defining a gapbetween each other; housing means formed with a passage extending towardsaid gap transversely to a plane passing through said axes and alsoformed with a feed duct having a discharge opening connected with saidpassage; a tamping means mounted in said passage for reciprocatingmovement between a retracted position, and an advanced position in whichthe leading end of said tamping mean confronts said gap and is locatedin close proximity to the surfaces of said rollers, said tamping meansin said retracted position uncovering said discharge opening, andcovering the same in said advanced position; feeding means in said ductfor transporting a material through said discharge opening into saidpassage so that the material accumulates under pressure in said passageand in the bight between said rollers in the region of said gap whilesaid tamping means is in said retracted position; and drive means forreciprocating said tamping means so that said accumulated mass isperiodically urged into said gap by said leading end of said tampingmeans.

7. An apparatus of the type described comprising, in combination, a pairof cooperating rotary rollers having parallel axes and defining a gapbetween each other; housing means formed with a passage bounded by wallsurfaces extending toward said gap transversely to a plane passingthrough said axes and also formed with a feed duct and having adischarge opening connected with said passage; resilient means forsupporting said roller for movement toward and away from each other sothat said gap is of variable width; a tamping plate means mounteed insaid passage slidably engaging said wall surfaces and for reciprocatingmovement between a retracted position, and an advanced position in whichthe leading end of said tamping plate means confronts said gap and islocated in close proximity to the surfaces of said rollers, said tampingplate means in said retracteed position uncovering said dischargeopening, and covering the same in said advanced position; feeding meansin said duct for transporting a material through said discharge openinginto said passage so that the material accumulates under pressure insaid passage and in the bight between said rollers in the region of saidgap while said tamping plate means is in said retracted position; anddrive means for reciprocating said tamping plate means so that saidaccumulated mass is periodically urged into said gap by said leading endof said tamping plate means.

8. A tamping arrangement comprising a pair of rotary rollers havingparallel axes and defining a gap between each other; a tamping deviceforming with said rollers 21 confined space communicating with said gap,and including wall means extending to said rollers and having anopening, and a tamping mean guided by said wall means for reciprocationtoward and away from said gap and between an advanced position in whichsaid tamping means is-located in the proximity of said gap and closessaid opening, and a retracted position in which said tamping means atleast partly uncovers said opening; and feeding means for feeding amaterial through said opening into said confined space whereby a mas ofparticles accumulates in the region of said gap while said tamping meansis in said retracted position so that the material is pressed into saidgap when said tamping means moves to said advanced position.

9. A tamping arrangement a claimed in claim 8 wherein said wall meansinclude a wall located adjacent said gap on the side of said tampingmeans remote from said opening and said feeeding means for holdingmaterial fed through said opening in the region of said gap.

10. A tamping arrangement as claimed in claim 8 wherein said tampingmeans has an operative end located in the proximity of said gap in saidadvanced position and having a length and width matching the length andwidth of said gap; and wherein said wall means form a passage forguiding said tamping means in a plane passing through said gapperpendicular to the axes of said rollers.

11. A tamping arrangement as claimed in claim 10 wherein said wall meansinclude a wall formed with said opening and bounding said passage on oneside, wherein said opening has a length matching the length of said gapand of said operative end of said tamping means; and wherein saidfeeding means is disposed along the length of said opening to feedmaterial into said confined space along the length of said gap.

12. A tamping arrangement as claimed in claim 8 wherein said feedingmeans includes a plurality of parallel transporting screws having axestransverse to the axes of said rollers.

13. A tamping arrangement as claimed in claim 8 comprising resilientmeans for mounting said rollers for movement toward and away from eachother so that the width of said gap varies with the pressure produced inthe material by said tamping means.

References Cited UNITED STATES PATENTS 2,144,911 1/1939 Cohn.

2,612,832 10/1952 Wiemer 241- -222 X 2,734,688 2/1956 Sloane 241-2222,828,924 4/1958 Ellsworth 241222 ANDREW R. JUHASZ, Primary Examiner.

1. AN APPARATUS FOR REDUCING THE SIZE OF PARTICLES, COMPRISING, INCOMBINATION, A PAIR OF COOPERATING ROTARY ROLLERS HAVING PARALLEL AXESAND DEFINING A GAP BETWEEN EACH OTHER; FEEDING MEANS FOR FEEDING THEPARTICLES TO SAID ROLLERS AND INCLUDING A FEED DUCT EXTENDING IN ADIRECTION SUBSTANTIALLY PARALLEL TO A PLANE EXTENDING THROUGH SAID AXESAND HAVING A DISCHARGE END LOCATED IN THE REGION OF SAID GAP SO THAT AMASS OF PARTICLES ACCUMULATES ON ONE SIDE OF SAID ROLLERS IN THE REGIONOF SAID GAP; A TAMPING MEANS DISPOSED AT SAID DISCHARGE END ON SAID SIDERECIPROCABLE PERPENDICULARLY TO SAID PLANE TOWARD AND AWAY FROM SAID GAPSO THAT THE MASS IS PERIODICALLY URGED INTO SAID GAP; PASSAGE MEANS FORSAID TAMPING MEANS HAVING AN OPENING FORMING SAID DISCHARGE END OF SAIDFEED DUCT, SAID TAMPING MEANS BEING MOVABLE BETWEEN AN ADVANCED POSITIONCLOSING SAID DISCHARGE END OF SAID DUCT, AND A RETRACTED POSITION INWHICH THE OPERATIVE END OF SAID TAMPING MEANS IS SPACED FROM SAID GAPUNCOVERING SAID DISCHARGE END AND STILL LOCATED IN SAID PASSAGE ANDMEANS FOR RECIPROCATING SAID TAMPING MEANS.